The esophagus is an organ within the neck that permits travel of food and saliva from the mouth to the stomach through peristalsis. It has a generally tubular shape consisting of multiple layers ranging from a mucosa layer on the lumen consisting primarily of epithelial cells to a muscular adventitia consisting primarily of smooth muscle cells, striated muscle cells and fibroblasts. The inner layer of muscle is oriented in a circumferential direction while the outer layer of muscle is oriented in a longitudinal direction (see FIG. 1). When at rest, the esophagus is nearly collapsed, but can expand to roughly 3 cm in diameter upon swallowing.
Peristalsis involves involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but occasionally in other hollow tubes of the body, that occur in progressive wavelike contractions. Peristaltic waves occur in the esophagus, stomach, and intestines. The waves can be short, local reflexes or long, continuous contractions that travel the whole length of the organ, depending upon their location and what initiates their action. In the esophagus, peristaltic waves begin at the upper portion of the tube and travel the whole length, pushing food ahead of the wave into the stomach. Particles of food left behind in the esophagus initiate secondary peristaltic waves that remove leftover substances. One wave travels the full length of the tube in about nine seconds. Peristaltic waves start as weak contractions at the beginning of the stomach and progressively become stronger as they near the distal stomach regions. The waves help to mix the stomach contents and propel food to the small intestine. Usually, two to three waves are present at one time in different regions of the stomach, and about three waves occur each minute.
In the large intestine (or colon), the peristaltic wave, or mass movement, is continuous and progressive; it advances steadily toward the anal end of the tract, pushing waste material in front of the wave. When these movements are vigorous enough to pass fecal masses into the rectum, they are followed by the desire to defecate. If feces are passed to the rectum and not evacuated from the body, they are returned to the last segment of the colon for longer storage by reverse peristaltic waves. Peristaltic waves are particularly important in helping to remove gas from the large intestine and in controlling bacterial growth by mechanically acting as a cleansing agent that dislodges and removes potential colonies of bacteria.
Partial loss or complete loss of peristalsis due to the loss of the esophagus, small intestine and/or large intestine due to cancer or other diseases can have a catastrophic, if not fatal, effect on an animal. A number of in vivo prostheses for luminal structures such as the esophagus are known. Typically these prostheses are formed by donor structures from cadavers or are manmade structures. However, these existing structures are subject to failure due to anastomotic stenosis, luminal stenosis, infection, dislocation, and migration, among other causes. Therefore, there is an ongoing need for artificial or prosthetic versions of organs such as the esophagus and intestinal tract that will provide the patient, human or otherwise, with a functioning replacement for the lost organ.